TRIPOLI, May 7 (Reuters) - Libyan government forces bombed large fuel storage tanks in the contested western city of Misrata, destroying the tanks and sparking a huge fire, rebels said on Saturday.

Misrata is the last remaining city in the west under rebel control. The port city has been under siege for more than two months. Hundreds have died in some of the war’s fiercest fighting between loyalists and rebels.

Rebels gave varying accounts of the Misrata bombardment but said the overnight attack, which hit fuel used for export as well as domestic consumption, came as a blow to their ability to withstand the siege.

“Four (fuel) tanks were totally destroyed and huge fire erupted which spread now to the other four. We cannot extinguish it because we do not have the right tools,” rebel spokesman Ahmed Hassan told Reuters.

“Now the city will face a major problem. Those were the only sources of fuel for the city. These tanks could have kept the city for three months with enough fuel,” he said by telephone.

Hassan said government forces used small planes normally used to spray pesticides for the overnight attack in Qasr Ahmed. He later told Al-Jazeera television that three helicopters bearing Red Crescent insignia conducted the attack.

Another rebel spokesman, who gave his name as Abdelsalam, said a government helicopter conducted a reconnaissance mission over the port and two hours later at around midnight local time government forces fired rockets that hit three fuel tanks belonging to the Brega Oil Company.

Rebels notified NATO about the planes before the attack but there was no response, Hassan said. Government forces last month flew at least one helicopter reconnaissance mission over Misrata, according to rebels. (Reporting by Mariam Karouny in Beirut and Joseph Nasr in Berlin; Writing by Matthew Bigg)